Applied Energy 88 (2011) 4197–4205
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Modeling water/lithium bromide absorption chillers in ASPEN Plus C. Somers a, A. Mortazavi a, Y. Hwang a,⇑, R. Radermacher a, P. Rodgers b, S. Al-Hashimi c a
Department of Mechanical Engineering, University of Maryland, College Park, MD, USA Department of Mechanical Engineering, The Petroleum Institute, Abu Dhabi, United Arab Emirates c Department of Chemical Engineering, The Petroleum Institute, Abu Dhabi, United Arab Emirates b
a r t i c l e
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Article history: Received 19 October 2009 Received in revised form 4 May 2011 Accepted 11 May 2011 Available online 1 June 2011 Keywords: ASPEN Plus Absorption chillers Absorption chiller modeling Energy efficiency Waste heat utilization
a b s t r a c t Absorption chillers are a viable option for providing waste heat-powered cooling or refrigeration in oil and gas processing plants, thereby improving energy efficiency. In this paper, single- and double-effect water/lithium bromide absorption chiller designs are numerically modeled using ASPEN. The modeling procedure is described and the results are compared to published modeling data to access prediction accuracy. Predictions for the single- and double-effect designs are within 3% and 5%, respectively of published data for all cycle parameters of interest. The absorption cycle models presented not only allow investigation into the benefits of using absorption chillers for waste heat utilization in the oil and gas industry, but are also generically applicable to a wide range of other applications. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction The oil and gas industry is a large consumer of thermal, mechanical and electrical energy, typically provided by gas turbines. Since gas turbines utilize only one third of their energy input for power generation, cogeneration is often used to generate thermal energy from the gas turbine waste heat. For example, about 72% of all natural gas plant capacity added in the US during 2009 was based on combined-cycle units [1]. However, conventional cogeneration recovers only a fraction of the waste heat by converting high grade waste heat to low grade to provide electricity, hot water and/or steam. The fraction of low grade waste heat not recovered could be utilized for powering an absorption refrigeration cycle to produce cooling. In this paper a modeling methodology is proposed and evaluated that combines waste heat utilization and absorption cooling. 1.1. Absorption chillers An absorption chiller is a closed loop cycle that uses waste heat to provide cooling or refrigeration. To date, the use of absorption chillers has been limited by their relatively poor efficiency at delivering cooling compared to vapor compressions cycles. An absorption chiller typically has a coefficient of performance (COP) between 0.5 and 1.5, while modern vapor compression cycles have COPs in excess of 3.0 [2,3]. However, absorption chillers ⇑ Corresponding author. Tel.: +1 301 405 5241; fax: +1 301 405 2025. E-mail address:
[email protected] (Y. Hwang). 0306-2619/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.apenergy.2011.05.018
are still widely used because they can utilize low temperature (
